Patch "x86/pti: Unbreak EFI old_memmap" has been added to the 4.14-stable tree

Patch "x86/pti: Unbreak EFI old_memmap" has been added to the 4.14-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    x86/pti: Unbreak EFI old_memmap

to the 4.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     x86-pti-unbreak-efi-old_memmap.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From de53c3786a3ce162a1c815d0c04c766c23ec9c0a Mon Sep 17 00:00:00 2001
From: Jiri Kosina <jkosina@suse.cz>
Date: Fri, 5 Jan 2018 22:35:41 +0100
Subject: x86/pti: Unbreak EFI old_memmap

From: Jiri Kosina <jkosina@suse.cz>

commit de53c3786a3ce162a1c815d0c04c766c23ec9c0a upstream.

EFI_OLD_MEMMAP's efi_call_phys_prolog() calls set_pgd() with swapper PGD that
has PAGE_USER set, which makes PTI set NX on it, and therefore EFI can't
execute it's code.

Fix that by forcefully clearing _PAGE_NX from the PGD (this can't be done
by the pgprot API).

_PAGE_NX will be automatically reintroduced in efi_call_phys_epilog(), as
_set_pgd() will again notice that this is _PAGE_USER, and set _PAGE_NX on
it.

Tested-by: Dimitri Sivanich <sivanich@hpe.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/nycvar.YFH.7.76.1801052215460.11852@cbobk.fhfr.pm
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/x86/platform/efi/efi_64.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -134,7 +134,9 @@ pgd_t * __init efi_call_phys_prolog(void
 				pud[j] = *pud_offset(p4d_k, vaddr);
 			}
 		}
+		pgd_offset_k(pgd * PGDIR_SIZE)->pgd &= ~_PAGE_NX;
 	}
+
 out:
 	__flush_tlb_all();
 


Patches currently in stable-queue which might be from jkosina@suse.cz are

queue-4.14/x86-pti-unbreak-efi-old_memmap.patch